FIGURE 18-24 The domain structure of cytoplasmic dynein. (a) The dynein heavy chain, consisting of over 4000 amino acid residues, has several distinct domains. Following the stem and linker domains are six AAA repeats (peach, numbered 1–6), with the stalk and its microtubule-binding domain between repeats 4 and 5. The protein ends in an α-helical domain that supports the stalk. (b) The six AAA repeats assume a structure like petals on a flower. Emerging from this structure is a coiled-coil stalk domain with a microtubule-binding site at the end. A number of additional subunits associate with the stem region and can link dynein to cargo through dynactin. See R. D. Vale, 2003, Cell 112:467.